With summer comes gardening, golf — and ozone pollution

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Finally. A few warm days have opened the door for Minnesota’s sweetest seasons: gardening, golf, lake swimming, softball. And, of course, never forget the fishing season.

How about the ozone season? Arghh! I would call that a dark side of summer, except you can’t see this odorless colorless gas that is a component of smog. But it’s coming. When temperatures rise in Minnesota, so does ozone pollution.

The problem in the Upper Midwest isn’t severe enough to spoil your summer. Cities like Los Angeles and Houston have a lot more to worry about than we do.

But ozone pollution is a growing worry everywhere. Minnesota officials expect to issue more ozone alerts this summer than they have in the past — not because the air will be more polluted but because the U.S. Environmental Protection Agency has raised the worry level by tightening the limits for ozone pollution.

Ozone pollution dangersOne reason for the heightened alert is spelled out in a report released today by the National Research Council. It concludes that even short-term exposure to ozone pollution is likely to contribute to premature deaths.

The report offers an extensive review of relevant studies rather than fresh research on the topic. It concludes: “Studies have yielded strong evidence that short-term exposure to ozone can exacerbate lung conditions, causing illness and hospitalization, and can potentially lead to death. The available evidence on ozone exposure and exacerbation of heart conditions, which is less abundant, points to another concern.”

The report calls repeatedly for more research into the effects of both short-term and long-term exposure to ozone, saying the risks appear to be higher and spread wider than previously believed.

“Although ozone was originally viewed as an urban pollutant (associated largely with such locations as Los Angeles), it is now recognized that ozone formation and transport over much larger areas result in increased exposures to humans nationwide,” the report said. “International transport of ozone exacerbates the problem.”

While the report leaves many unanswered questions, what it does for now is bolster arguments the EPA already had made that the costs of ozone pollution are higher than most experts thought. One reason there had been gaps in the knowledge about ozone pollution and health is that ozone typically comes mixed with other pollutants that exacerbate the same health problems.

The Clean Air Act requires the EPA to issue and review periodically the National Ambient Air Quality Standards for six pollutants, one of which is ozone in the lower atmosphere. The EPA had requested the report in connection with that process.

Key sources of pollutionThe non-scientific public can be forgiven for some confusion about ozone. It is good in its proper place. Naturally occurring ozone in the upper atmosphere helps protect the Earth’s surface from ultraviolet radiation.

The problem begins at ground level, where elevated concentrations can irritate the respiratory system, impair lungs, aggravate asthma and increase susceptibility to respiratory illnesses such as pneumonia and bronchitis. Children, active adults, and people with respiratory diseases are particularly sensitive to ozone.

In Minnesota, ozone has been considered to be less of a problem than another category of air pollutant called fine particles, said Mark Sulzbach who is an information officer for the Minnesota Pollution Control Agency. And it’s not a problem in winter.

“Ozone is a summer issue,” Sulzbach said. “Pretty much May through September is our ozone season.”

Ozone is created when “precursors” such as nitrogen oxides and volatile organic compounds react in the kind of weather Minnesota sees on a sweltering summer afternoon.

The precursors come from cars, trucks, construction equipment, factories, power plants, and even lawnmowers. Some also are emitted naturally by soil and vegetation.

Minnesota has taken many steps to reduce the emissions and keep ozone levels within the limits federal regulators consider acceptable.

And state health officials have spelled out the precautions people should take when ozone levels are elevated. They include avoiding heavy outdoor exertion — even for the fit, but especially for those with asthma or other respiratory problems and for kids who play outdoors a lot. It’s best to walk instead of run or else exercise inside.

How do you know when the levels are elevated? The Minnesota Pollution Control Agency posts information on its Air Quality Index page. You also can sign up to get email notices of alerts.